Gastrointestinal malignancies, including adenocarcinoma of the esophagus, stomach, colon, and rectum, are a leading cause of cancer and cancer-related mortality worldwide. GC-C is a transmembrane receptor expressed only on the apical membranes of intestinal enterocytes in normal, healthy adults and by primary and metastatic tumor cells of gastric, esophageal and colorectal adenocarcinoma. Conzelmann, M., et al., Cytokeratin 20 and guanylyl cyclase C mRNA is largely present in lymph node and liver specimens of colorectal cancer patients. Int J Cancer, 2003. 107(4): p. 617-28; Cagir, B., et al., Guanylyl cyclase C messenger RNA is a biomarker for recurrent stage II colorectal cancer. Ann Intern Med, 1999. 131(11): p. 805-12; Bustin, S. A., et al., Quantification of cytokeratin 20, carcinoembryonic antigen and guanylyl cyclase C mRNA levels in lymph nodes may not predict treatment failure in colorectal cancer patients. Int J Cancer, 2004. 108(3): p. 412-7; Pearlman, J. M., et al., A splice variant of the transcript for guanylyl cyclase C is expressed in human colon and colorectal cancer cells. Dig Dis Sci, 2000. 45(2): p. 298-305; Waldman, S. A., et al., Use of guanylyl cyclase C for detecting micrometastases in lymph nodes of patients with colon cancer. Dis Colon Rectum, 1998. 41(3): p. 310-5; Salto-Tellez, M., et al., Intrinsic variability in the detection of micrometastases in lymph nodes for re-staging of colorectal cancer. effect of individual markers and tissue samples. Eur J Cancer, 2003. 39(9): p. 1234-41; Chen, G., et al., Detection of occult metastasis in lymph nodes from colorectal cancer patients: a multiple-marker reverse transcriptase-polymerase chain reaction study. Dis Colon Rectum, 2004. 47(5): p. 679-86; Notarnicola, M., et al., K-ras and p53 mutations in DNA extracted from colonic epithelial cells exfoliated in faeces of patients with colorectal cancer. Dig Liver Dis, 2000. 32(2): p. 131-6; Hugues, M., et al., Identification and characterization of a new family of high-affinity receptors for Escherichia coli heat-stable enterotoxin in rat intestinal membranes. Biochemistry, 1991. 30(44): p. 10738-45; Carrithers, S. L., et al., Escherichia coli heat-stable enterotoxin receptors. A novel marker for colorectal tumors. Dis Colon Rectum, 1996. 39(2): p. 171-81; Carrithers, S. L., et al., Guanylyl cyclase C is a selective marker for metastatic colorectal tumors in human extraintestinal tissues. Proc Natl Acad Sci USA, 1996. 93(25): p. 14827-32; Carrithers, S. L., et al., Escherichia coli heat-stable toxin receptors in human colonic tumors. Gastroenterology, 1994. 107(6): p. 1653-61; Bustin, S. A., et al., Detection of cytokeratins 19/20 and guanylyl cyclase C in peripheral blood of colorectal cancer patients. Br J Cancer, 1999. 79(11-12): p. 1813-20; Pitari, G. M., et al., Guanylyl cyclase C agonists regulate progression through the cell cycle of human colon carcinoma cells. Proc Natl Acad Sci USA, 2001. 98(14): p. 7846-51; Tien, Y. W., et al., Simultaneous detection of colonic epithelial cells in portal venous and peripheral blood during colorectal cancer surgery. Dis Colon Rectum, 2002. 45(1): p. 23-9; Park, J., et al., Ectopic expression of guanylyl cyclase C in adenocarcinomas of the esophagus and stomach. Cancer Epidemiol Biomarkers Prev, 2002. 11(8): p. 739-44; Pitari, G. M., et al., Bacterial enterotoxins are associated with resistance to colon cancer. Proc Natl Acad Sci USA, 2003. 100(5): p. 2695-9; Vlems, F. A., et al., Investigations for a multi-marker RT-PCR to improve sensitivity of disseminated tumor cell detection. Anticancer Res, 2003. 23(11A): p. 179-86; Tien, Y. W., et al., The role of gelatinase in hepatic metastasis of colorectal cancer. Clin Cancer Res, 2003. 9(13): p. 4891-6; Chen, W. S., et al., Impact of Circulating Free Tumor Cells in the Peripheral Blood of Colorectal Cancer Patients during Laparoscopic Surgery. World J Surg, 2004; and Tien, Y. W., et al., Intravasation-Related Metastatic Factors in Colorectal Cancer. Tumour Biol, 2004. 25(1-2): p. 48-55, which are each incorporated herein by reference.
GCC has been identified previously as a specific marker and target for GI malignancies. Identification of the presence of GCC in ectopic sites, for example lymph nodes or blood, can be used as a marker to identify the presence of occult micrometastases of esophageal, gastric, colonic, or rectal cancers. One method to detect the presence of GCC is to quantify the amount of binding of a natural ligand of GCC, such as ST, in tissues. Also, GCC appears to be a highly-specific target to which can be directed novel imaging and therapeutic agents to treat metastatic esophageal, gastric, colonic, and rectal cancers. Indeed, diagnostic or therapeutic agents can be targeted to GCC-expressing tumors by their conjugation to GCC ligands such as ST.
U.S. Pat. No. 5,518,888 issued May 21, 1996 to Waldman, PCT application PCT/US94/12232 filed Oct. 26, 1994, U.S. application Ser. No. 08/467,920 filed Jun. 6, 1995, and U.S. application Ser. No. 08/583,447 filed Jan. 5, 1996, which are each incorporated herein by reference, disclose that metastasized colorectal tumors can be targeted for delivery of active compounds by targeting ST receptors (also referred to as guanylin cyclase C or GCC). The presence of ST receptors on cells outside of the intestinal tract as a marker for colorectal cancer allows for the screening, identification and treatment of individuals with metastasized colorectal tumors. ST receptors may also be used to target delivery of gene therapeutics and antisense compounds to colorectal cells.
U.S. Pat. No. 5,601,990 issued Feb. 11, 1997 to Waldman, PCT application PCT/US94/12232 filed Oct. 26, 1994, and PCT application PCT/US97/07467 filed May 2, 1997, which are each incorporated herein by reference, disclose that detection of evidence of expression of ST receptors in samples of tissue and body fluid from outside the intestinal track indicate metastasized colorectal cancer.
U.S. Patent Application Publication No. 20010029019 published Oct. 11, 2001, which is each incorporated herein by reference, discloses that primary and metastasized stomach and esophageal cancer tumors can be targeted for delivery of active compounds by targeting GCC. GCC serves as a marker for primary and metastasized stomach and esophageal cancer and allows for the screening, identification and treatment of individuals with primary and metastasized stomach and esophageal cancer. GCC is also be used to target delivery of gene therapeutics and antisense compounds to primary and metastasized stomach and esophageal cancer.
GCC regulates the balance of proliferation and differentiation of the epithelium in intestine. The intestinal epithelium is dynamic, with a well-defined vertical axis extending from the crypt depths, in the wall of the intestine, to the tips of villi which project out into the lumen of the intestine. Epithelial cells are “born” at the bottom of crypts as daughter cells produced by intestinal stem cells. These daughter cells continue to divide (proliferate) and their progeny migrate up the wall of the crypt toward the tip of the villus. Along this migration, the cells shift from proliferation to differentiation to become fully-functional mature enterocytes with the capacity to perform the normal functions of the gut including digestion, absorption and secretion. Once at the tip, these cells slough off into the lumen of the intestine and die. Thus, the intestinal epithelium turns over ˜every three days. GCC and its endogenous ligands appear to be one of the factors that shifts epithelial cells from proliferation to differentiation along the crypt-villus axis. Indeed, GCC ligands inhibit the proliferation of these cells and change their gene expression pattern to a more terminally-differentiated state.
The GC-C protein has not been detected in any non-cancerous tissue outside of the intestine and is only found on tumors of gastrointestinal origin. Of particular importance to this proposal, the detection of GC-C mRNA has not been reported in any colorectal cancer metastatic tissues, i.e. non-colorectal tissue where metastatic colorectal cancer is often detected. For normal individuals, the presence of GC-C mRNA has not been described in the published literature for the metastatic sites of colorectal, gastric or esophageal cancer (i.e., liver, lung, bone, brain), but it has been described in the proximal tubule cells of the kidney (Sindice, A., et al., Guanylin, uroguanylin, and heat-stable enterotoxin activate guanylate cyclase C and/or a pertussis toxin-sensitive G protein in human proximal tubule cells. J Biol Chem, 2002. 277(20): p. 17758-64, which is incorporated herein by reference), exocrine duct cells of the pancreas (Kulaksiz, H., et al., Guanylin in the human pancreas' a novel luminocrine regulatory pathway of electrolyte secretion via cGMP and CFTR in the ductal system. Histochem Cell Biol, 2001. 115(2): p. 131-45, which is incorporated herein by reference), submandibular glands (Kulaksiz, H., et al., Guanylin and functional coupling proteins in the human salivary glands and gland tumors: expression, cellular localization, and target membrane domains. Am J Pathol, 2002. 161(2): p. 655-64, which is incorporated herein by reference), the bile duct (Kulaksiz, H., et al., Guanylin regulates chloride secretion in the human gallbladder via the bile fluid. Gastroenterology, 2004. 126(3): p. 732-40. which is incorporated herein by reference) and at trace levels in CD34+ stem cells (Fava, T. A., et al., Ectopic expression of guanylyl cyclase C in CD34+ progenitor cells in peripheral blood. J Clin Oncol, 2001. 19(19): p. 3951-9). A common theme for each of these anatomical locations, except CD34+ cells, is that GC-C is separated from the blood and lymphatic systems by tight junctions analogous to that found in the intestine.
Diarrheal diseases are the fourth leading cause of mortality worldwide, responsible for about 20 million deaths each year. Such diseases are the leading cause of pediatric mortality worldwide, particularly affecting children under 5 years of age. Further, diarrheal diseases are responsible for ˜25% of the growth retardation observed in children raised in under-developed, compared to developed, nations. One major cause of diarrheal disease are organisms producing heat-stable enterotoxins (STs), a family of structurally-related peptides produced by different organisms including, but not limited to, E. coli, Yersinia, Enterobacter, and Vibrio. This family of structurally-related ST peptides is homologous to the endogenous peptides guanylin and uroguanylin produced in mammalian intestine. ST-producing organisms are a major cause of endemic diarrhea in under-developed countries, the leading cause of travelers' diarrhea, and the leading cause of diarrheal disease in agriculturally-important animal populations (scours) in developed and under-developed countries. It is estimated that the annual incidence of ST-induced diarrheal disease numbers in the billions in animals and humans. ST induces diarrhea by binding to GCC, which is selectively expressed in brush border membranes of intestinal epithelial cells and the presumed receptor for the endogenous ligands guanylin and uroguanylin. Interaction of ST, or the endogenous ligands guanylin and uroguanylin, with GCC activates that receptor resulting in the production of intracellular cyclic GMP. Cyclic GMP, through a signaling cascade induces the secretion of salt and water into the lumen of the intestine, resulting in diarrhea. It has been suggested that one function for the endogenous ligands guanylin and uroguanylin in normal physiology is the regulation of fluid and electrolyte homeostasis in intestine, and the hydration of intestinal contents (e.g. stool).
Over the past 20 to 30 years, attempts have been made to design ligands that antagonize GCC. Such a compound of the invention would be useful in the detection of GCC on cells, as a targeted diagnostic and therapeutic agent in cases of GI malignancies, and in the treatment of diarrheal diseases of animals and humans. Moreover, such a compound of the invention might have application in cases requiring intestinal adaptation, wherein the epithelium requires rapid regeneration following an insult, for example chemical or ischemic damage. Previous structure-function studies of GCC ligands were unrevealing with respect to the discriminating the structural determinants required for receptor binding from those required for agonist activation (e.g. cyclic GMP production).
There is a need for compounds that bind to GCC and activate the GCC signal pathway and there is a need for compounds which bind to GCC but do not activate the GCC signal pathway.